Research Of The Diamond Film Nucleation And Growth On The Mo Substrates By HFCVD

The diamond thin films were deposited on Mo substrates via hot filament chemical vapor deposition(HFVCD).The surface morphology and the texture of the films were investigated by scanning electron microscope(SEM)and X-ray diffraction(XRD)respectively. Investigations had been made on the relationship among deposition parameters and the nucleation density and growth of CVD diamond films. The chemical processes in vapor deposition of diamond were analyzed via thermodynamics calculation method.Conclusion can be drawn as following:1.The optimization deposition parameters of diamond film deposited on Mo substrates are:Hot filament temperature 2200±50℃, Substrate temperature 770±50℃,Pressure 3.5KPa and V_CH4/V_H2 =3/97.2.The carbon concentration has effect on the surface nucleation density of diamond films.The nucleation density drastically increases when the carbon concentration is between 2%and 3%,while the nucleation density is quite low as carbon concentration is lower than 2%. The nucleation density decreases on further increasing carbon concentration over 3%.The growth process of crysyal accelerates when the carbon concentration increases,while the nucleation density decreases under the effect of excessive growth.3.The deposition pressure has the similar effect tendency on nucleation density.The nucleation density drastically increases when the deposition pressure is between 3.5KPa and 4KPa,while the nucleation density is quite low as deposition pressure is lower than 3KPa.The nucleation density decreases on further increasing deposition pressure over 4KPa.4.In the variation of carbon concentration deposition process,the high-density 2×10⁸ cm^-2could be obtained by a longer period of time of high carbon concentration then quickly reducing,while the surface nucleation rate is lower by the gentler reduction of carbon concentration.5.The results of thermodynamics calculation predicted the composition of the vapor phases.When the deposition parameters are Pressure 3.5KPa and V_CH4/V_H2=5/95,the C₂H₂ is the main group in the vapor phases.Atomic hydrogen has a great content in the temperature range of 2100 to 2300℃,which is beneficial to the diamond film deposition.